And what of Tutankhamun's mother? To our surprise, the DNA of the so-called Younger Lady (KV35YL), found lying beside Tiye in the alcove of KV35, matched that of the boy king. More amazing still, her DNA proved that, like Akhenaten, she was the daughter of Amenhotep III and Tiye. Akhenaten had conceived a son with his own sister. Their child would be known as Tutankhamun.

With this discovery, we now know that it is unlikely that either of Akhenaten's known wives, Nefertiti and a second wife named Kiya, was Tutankhamun's mother, since there is no evidence from the historical record that either was his full sister. We know the names of five daughters of Amenhotep III and Tiye, but we will probably never know which of Akhenaten's sisters bore him a child. But to me, knowing her name is less important than the relationship with her brother. Incest was not uncommon among ancient Egyptian royalty. But I believe that in this case, it planted the seed of their son's early death.

The results of our DNA analysis, published in February in the Journal of the American Medical Association, convinced me that genetics can provide a powerful new tool for enhancing our understanding of Egyptian history, especially when combined with radiological studies of the mummies and insights gleaned from the archaeological record.

Nowhere is this more evident than in our quest to understand the cause of Tutankhamun's death. When we began the new study, Ashraf Selim and his colleagues discovered something previously unnoticed in the CT images of the mummy: Tutankhamun's left foot was clubbed, one toe was missing a bone, and the bones in part of the foot were destroyed by necrosis—literally, "tissue death." Both the clubbed foot and the bone disease would have impeded his ability to walk. Scholars had already noted that 130 partial or whole walking sticks had been found in Tutankhamun's tomb, some of which show clear signs of use.